Badger Beth is the story of Liz Cooper, a young orphan who lives with her aunt, uncle and cousin in the fictional English village of Dalesbury. Liz is out cycling when she meets a young badger cub. After discovering that the cub's mother has been killed, Liz takes her in, and names her Beth (as Liz's name is Elizabeth, and she has always wanted to be called Beth). But how long can she keep the animal hidden from her family?
Liz initially hides Beth in her uncle Simon's garden shed. Her cousin Sandra soon stumbles across the secret pet, and blackmails Liz - she will keep the secret, but only if Liz performs all manner of chores for her, including doing her homework. She says that as her parents will not even allow cats and dogs in the house, they will be furious if they find the badger.
It isn't long before the badger escapes from the shed, and tunnels into the garden next door, munching her way through the neighbour's prize vegetables. Liz's uncle then announces that he is knocking the shed down as he no longer needs it, leading Liz and Sandra to hide Beth on the grounds of their school.
Liz escapes for a second time while hidden at the school, and after wandering onto the pitch during a girls hockey match, she falls into the hands of Mr Gould, the groundskeeper. After confronting the man, Liz discovers that he has a friend who pays for rare animal specimens, and plans to have Beth stuffed and mounted. She hits the man with her hockey stick, snatches the badger, and runs away.
Shaken by the experience, the girls decide to enlist the help of their neighbour in finding Beth a safer, more permanent home. But Beth flees once more, and finds her way into an underground cave where a group of potholers are stranded. After helping the men to escape, Liz and Beth are interviewed and photographed for the local paper - and their secret is exposed!
Fortunately, Liz's aunt and uncle are very understanding, and Beth is eventually taken in by an animal sanctuary. Rather that punish Liz, both her family and her headmistress are extremely proud of her. The tale ends as Liz stumbles across her cousin Sandra feeding some secret mice she has found. Liz agrees to return the favour and keep her secret - if Sandra tidies her room and does her homework for her.